This invention relates generally to electromagnetically operated brakes for electric motors, and deals more particularly with an electromagnetically operated motor brake having an automatic adjustment for the gap provided between the electromagnetic pole piece and its associated armature to compensate for wear in the friction disc of the brake.
Electromagnetically operated motorbrakes generally include biasing means for urging an armature toward a pressure plate so as to prevent rotation of a brake disc that turns with the shaft of an electric motor, and an electromagnet is adapted to pull the armature toward the pole piece and away from the disc and pressure plate when energized.
One problem associated with motorbrakes of this type is that they require periodic readjustment to maintain a predetermined gap between the armature and the pole piece of the electromagnetic device. This gap can increase due to wear of the friction disc.
Automatic wear compensation devices have been installed on motorbrakes in an attempt to minimize or eliminate the requirement for periodic adjustments to maintain acceptable operating performance of motorbrakes of this type. One such device is illustrated in the German publication OS No. 2314483 dated Oct. 3, 1974 entitled solenoid released spring disc brake. In this German disclosure the spring loaded stationary brake armature disc is mounted between the solenoid housing and a friction disc rotating on the shaft, and there is a stationary reaction plate on the other side of the shaft disc. Bolts are mounted in the solenoid housing and armature, and protrude into bores in the reaction plate. The bores contain axially lockable devices securing the reaction plate in position in relation to the bolts, and are automatic in operation. The locking devices allow the reaction plate to move toward the solenoid body as wear of the friction disc must be taken up.
In another prior art U.S. Pat. No. 3,613,849 issued to Pape, an electromagnetic brake releasing device is disclosed that also has as automatic adjusting device designed to compensate for wear of the friction elements or pads. An armature is associated with a magnetic core to move toward and away from the friction elements or pads, and the adjusting device includes looking elements that permit the core to slide freely on guide bolts only toward the armature and toward the friction elements, and to slide toward the magnetic core only the distance of the armature stroke.